Question

Why doesn’t this code compile:

public class FakeESBSingleMessage<T> : IBusEnabledClass
{
    private Action<T> SubscribedAction { get; set; }

    #region IBusEnabledClass

    public void Publish<T>(T message)
    {
        SubscribedAction(message);
    }

    public void Subscribe<T>(string ID, Action<T> action)
    {
        SubscribedAction = action;
    }

    #endregion
}

It give the following errors:

Error 37 Argument 1: cannot convert from ‘T [..FakeESBSingleMessage.cs(8)]’ to ‘T’ ..FakeESBSingleMessage.cs 16 30
Error 39 Cannot implicitly convert type ‘System.Action [mscorlib.dll]’ to ‘System.Action [mscorlib.dll]’ ..FakeESBSingleMessage.cs 21 32
Error 36 Delegate ‘System.Action’ has some invalid arguments ..\FakeESBSingleMessage.cs 16 13

I’m trying to create a fake ESB component for testing, that saves the delegate passed on Subscribe and calls it when publish is called.

Answer 1

You get the compile error because your Publish and Subscribe messages define a new type parameter T, rather than using the one defined in the class. Try this instead:

public class FakeESBSingleMessage<T> : IBusEnabledClass
{
    private Action<T> SubscribedAction { get; set; }

    #region IBusEnabledClass

    public void Publish(T message)
    {
        SubscribedAction(message);
    }

    public void Subscribe(string ID, Action<T> action)
    {
        SubscribedAction = action;
    }

    #endregion
}